Device built into a cylinder head for controlling amount of air fed into the intake of a turbocharged internal combustion engine and method using such a device

ABSTRACT

The present invention relates to a device for controlling the amount of air fed into the intake of a charged internal combustion engine, said engine comprising two exhaust gas outlets ( 32, 36 ) each connected to an exhaust manifold ( 30, 34 ) of a group of at least one cylinder ( 12   1,    12   2   , 12   3   , 12   4 ), said device comprising a charging device ( 38 ) comprising a turbocompressor having a dual-inlet ( 46, 48 ) turbine ( 40 ) connected to said exhaust gas outlets and an external air compressor ( 44 ), and at least one duct for partially transferring compressed air from the compressor to the turbine inlets. 
     According to the invention, the partial transfer duct ( 100, 102; 110, 112 ) is integrated into the cylinder head and comprises throttling means ( 74, 76 ) controlling the circulation of compressed air in said duct.

The present invention relates to a device for controlling the amount of air fed into the intake of a turbocharged internal combustion engine, in particular a stationary engine or an engine for an automotive or industrial vehicle, and a method for controlling the quantity of air for such an engine. In particular, the majority of the elements of the device and in particular the various ducts are arranged integrated in the cylinder head of the engine.

As is widely known, the power delivered by an internal combustion engine is dependent on the quantity of air introduced into the combustion chamber of said engine, the air quantity itself being proportional to the density of the air.

Thus it is usual to increase the quantity of air by compressing the external air before it is introduced into the combustion chamber. This operation, called charging, may be performed by various means such as a turbocompressor or a driven compressor, which may be centrifugal or volumetric.

In the case of charging by a turbocompressor, the latter comprises a rotating turbine with single or double flow, connected by a shaft to a rotating compressor. The exhaust gases from the engine pass through the turbine which is then driven in rotation. This rotation is then transmitted to the compressor which, by its rotation, compresses the external air before it is introduced into the combustion chamber.

As is best described in French patent application number 2 478 736, in order to significantly increase this quantity of compressed air in the combustion chamber of the engine, it is provided to further increase the compression of the external air by the compressor.

This is achieved more particularly by increasing the rotation speed of the turbine and hence of the compressor.

To do this, part of the compressed air leaving the compressor is diverted in order to be fed directly to the inlet of the turbine where it mixes with the exhaust gases. Then a large quantity of fluid (mixture of compressed air and exhaust gas) passes through the turbine, which allows an increase in the rotation speed of the turbine and consequently of the compressor. This increase in compressor speed then allows an increase in the pressure of the external air which will be compressed in this compressor and introduced into the combustion chamber of the engine.

In this way, the compressed air has a greater density, which allows an increase in the quantity of air contained in the combustion chamber.

This type of charged engine, although satisfactory, nonetheless has substantial drawbacks.

In fact the flow of compressed air fed to the inlet of the turbine is not correctly controlled, which can lead to a malfunction of the engine.

Thus for example, if too great a quantity of compressed air is diverted to the turbine inlet, the exhaust gases entering the turbine are cooled too greatly by this air, which leads to a reduction in the total efficiency of the charging.

The present invention proposes to remedy the above-mentioned drawbacks with a device for controlling the quantity of air fed to the intake of a charged internal combustion engine, which allows all the power demands of the engine to be fulfilled. Furthermore, the embodiment of the present invention is limited to modifications of the engine cylinder head, which minimizes its impact to the environment of the engine. The conventional compressed air loop is not modified.

The invention presented here also allows a transfer of the compressed air from the intake to the exhaust even when the mean pressure of the compressed air at the intake is lower than that of the exhaust gases. It is sufficient merely for phases to exist during the engine operating cycle in which the pressure at the intake is higher than that at the exhaust.

To this end, the present invention concerns a device for controlling the amount of air fed into the intake of a charged internal combustion engine, said engine comprising two exhaust gas outlets each connected to an exhaust manifold of a group of at least one cylinder, said device comprising a charging device comprising a turbocompressor having a dual-inlet turbine connected to said exhaust gas outlets and an external air compressor, and at least one duct for partially transferring compressed air from the compressor to the turbine inlets, characterized in that the partial transfer duct is built into the cylinder head of the engine between an intake and an exhaust connected to the turbine inlets, and has throttling means controlling the circulation of transferred compressed air.

The partial transfer duct may comprise a non-return flap.

The device may comprise at least two partial transfer ducts integrated into the cylinder head and connected to two exhaust outlets of said cylinder head in communication with the two turbine inlets.

The partial transfer duct may connect the intake and exhaust of a same cylinder.

The partial transfer duct may connect the intake of one cylinder and the exhaust of another cylinder.

The throttling means may comprise proportional valves.

The device may comprise means for controlling the proportional valves.

The invention also concerns a method for controlling the amount of compressed air fed into the intake of a charged internal combustion engine, said engine comprising two exhaust gas outlets each connected to an exhaust manifold of a group of at least one cylinder, said device comprising a charging device with a turbocompressor having a dual-inlet turbine connected to said exhaust gas outlets and an external air compressor, and at least one duct for partially transferring compressed air from the compressor to the turbine inlets, characterized in that it consists of arranging said duct in the cylinder head of the engine between an intake and an exhaust connected to the turbine inlets, and introducing part of the compressed air leaving the compressor via said duct into the exhaust gas turbine inlets.

The method may consist of arranging at least two transfer ducts in the cylinder head and controlling the circulation of compressed air in each of the ducts by throttling means.

Other characteristics and advantages of the invention will appear from reading the description below, which is given purely for illustrative purposes and is not imitative, and to which the following drawings are attached:

FIG. 1 which illustrates an internal combustion engine with a diagrammatic representation of the principle of the charging device according to the invention;

FIG. 2 which shows more precisely an embodiment of the internal combustion engine with its charging device comprising a transfer duct incorporated in the cylinder head.

On FIG. 1, the internal combustion engine 10 comprises at least two cylinders, here four cylinders referenced 12 ₁ to 12 ₄ from the left of the figure.

Preferably, the engine is a direct-injection internal combustion engine, in particular of the diesel type, but this in no way excludes any other type of internal combustion engine.

Each cylinder comprises intake means 14 with at least one intake valve 16, here two intake valves each controlling an intake tube 18. The intake tubes 18 open into an intake manifold 20 supplied with intake air, such as compressed air, by an intake duct 22.

This cylinder also comprises exhaust means 24 for the combusted gases with at least one exhaust valve 26, here also two valves each controlling one exhaust tube 28.

In the example illustrated, the engine is intended to function with a firing sequence of 1-3-4-2.In view of this firing sequence, the exhaust tubes of the first cylinder 12 ₁ and the second cylinder 12 ₄, which form a first group of at least one cylinder, are connected to a first exhaust manifold 30 with a first exhaust gas outlet 32. The exhaust tubes of the third and fourth cylinders 12 ₂ and 12 ₃, which form a second group of at least one cylinder, are connected to a second exhaust manifold 34 which comprises a second exhaust gas outlet 36.

The two exhaust gas outlets lead to a turbocompressor 38 for compressing the air, and more particularly to the expansion turbine 40 of this turbocompressor.

As illustrated on FIG. 1, the turbocompressor is a dual-inlet turbocompressor, better known as a twin scroll turbocompressor.

This type of turbocompressor comprises the expansion turbine 40 swept by the exhaust gases, which is connected in rotation by a shaft 42 to a compressor 44.

At the turbine, the inlet of the exhaust gases is divided into two sections, a first inlet section 46 connected to the first exhaust gas outlet 32 of the first manifold 30, and a second inlet section 48 connected to the second exhaust gas outlet 36 of the second exhaust manifold 34.

The evacuation of the gases 50 from the turbine 40 is conventionally connected to the exhaust pipe 52 of the engine.

The compressor 44 of the turbocompressor 38 comprises an external air intake 54 supplied by an intake pipe 56. The compressed air outlet 58 of this compressor is connected to the intake duct 22 of the intake manifold 20 by a pipe 60.

Advantageously, a cooling radiator 62 for the compressed air may be placed on the pipe 60 between the compressor and the duct 22.

As best shown on FIG. 1, a transfer duct 64 allows circulation of part of the compressed air leaving the compressor 44 towards the intakes 46 and 48 of the turbine.

This configuration, shown on FIG. 1, better illustrates the principle of the invention by clearly describing the different compressed air circuits; however, the present invention is produced according to FIG. 2, wherein the scavenging ducts are arranged in the engine cylinder head.

According to FIG. 1, the partial transfer duct starts on the pipe 60 at an intersection point 66 between the compressor and the cooling radiator 62, and then separates from a branch point 68 into two branches 70 and 72. The branch 70 leads to the inlet 46 of the turbine via its junction with the first exhaust gas outlet 32, and the branch 72 leads to the other inlet 48 of the turbine via its junction with the exhaust gas outlet 36.

Each branch comprises throttling means 74 and 76, such as a proportional valve, controlled by a control means 78 which may be common to both throttling means. This valve thus allows control of the circulation of compressed air circulating in the branch.

Advantageously, each branch also comprises a non-return flap 80 and 82 which prevents the circulation of compressed air from the branch to the compressor by preventing the communication of the two branches.

This configuration therefore allows, during operation of the engine, the benefit of exhaust zones of low pressure prevailing locally in the exhaust manifold, in order to introduce compressed air into the turbine and thus increase the flow of this turbine and consequently of the compressor. This also allows a more effective charging at low rotation speeds.

During operation, if large quantities of air are required in the cylinders, valves 74 and 76 are commanded to open in order to introduce compressed air from the compressor 44 into the turbine 40.

The compressed air leaving the compressor 44 circulates in the duct 64 and then in the branches 70 and 72 opening into the exhaust gas inlets 46 and 48 of the turbine 40, bringing a surplus of fluid to this turbine.

Thus not only do the exhaust gases from outlets 30 and 36 pass through the turbine, but also compressed air which is added to this gas. Therefore the rotation of the turbine is increased, which leads to an increase in rotation of the compressor and consequently an increase in pressure of the compressed air leaving this compressor.

Naturally, valves 74 and 76 are controlled by the control means 78 so as to deliver the quantity of compressed air to the turbine which meets the charging needs of the engine.

FIG. 2 describes an exemplary embodiment of the invention. Here, the compressed air loop at the engine intake is not modified between the outlet of the compressor 38 and the intake tubes 18. Also, the exhaust loop is not modified, in particular the part supplying the turbine 14.

The present invention entails incorporation of partial transfer ducts for compressed air integrated into the body of the engine cylinder head.

Thus at piston 124, a partial transfer duct 100 connects the duct of the cylinder head into which the intake tube opens, to the exhaust duct at the cylinder head. This partial transfer duct contains a valve 74 for controlling the flow of air, and a non-return flap 80 to prevent the back flow of exhaust gases to the intake. This flap may be arranged upstream or downstream of the valve or even integrated in the valve 76.

This arrangement allows the introduction of compressed air from the compressor 44 to the inlet 46 of the turbine 40 through the cylinder 12 ₁.

Advantageously, another partial transfer duct 102 may be provided at the piston 12 ₂, which connects the duct of the cylinder head into which the intake tube opens, to the exhaust duct. A valve 76 is provided on this partial transfer duct for controlling the flow of air, and a non-return flap 82 to prevent the back flow of exhaust gas to the intake.

This arrangement allows the introduction of compressed air from the compressor 44 to the inlet 48 of the turbine 40 through the cylinder 12 ₁.

In a variant, from piston 123, another partial transfer duct 110 connects an intake to the exhaust duct of piston 122. Thus the partial transfer of compressed air opens into the exhaust tube 34 which feeds the inlet 48 of the turbine 40. Like the transfer duct 100, the duct 112 is equipped with a flow control valve 76 and a non-return flap 82.

Also, another partial transfer duct 112 may be provided at piston 12 ₄, which connects an intake to the exhaust duct of piston 12 ₁. This other duct is equipped with a valve 76 and a non-return flap 82. In this case, the partial transfer of compressed air opens into the exhaust tube 30 which feeds the inlet 46 of the turbine 40.

As has been described with reference to FIG. 1, control means are connected to all control valves, so that the compressed air flows injected via the partial transfer ducts can be synchronized.

The embodiments are not limited to those exemplified on FIG. 2; other equivalent configurations of transfer ducts in the cylinder head may be considered, in particular depending on the type of cylinder head or engine.

It is thus possible to provide the system either on all ducts (then requiring one system per duct) and on all cylinders (then requiring one system per duct and per cylinder), or on a limited number of ducts and/or cylinders.

It is also possible to group the ducts of the same cylinder or several cylinders if the size of the cylinder head allows, or to cross the ducts between cylinders so as to maximize the short-circuited flows.

In all cases, the flaps may be arranged upstream or downstream of the valve or integrated in the valve.

The partial transfer ducts may be created at the same time as casting of the cylinder head with space reserved for the throttling equipment, or by machining of the ducts after production of the cylinder head.

Naturally, a mixed embodiment is also possible.

It remains within the scope of the present invention if the partial transfer ducts integrated in the cylinder head are produced by tubes arranged on the cylinder head and connected to the intake duct and the exhaust duct as described above, insofar as the device is integrated between the intake and exhaust manifolds, i.e. without affecting the conventional intake loop and exhaust loop. 

1. A device for controlling the amount of air fed into the intake of a charged internal combustion engine, said engine comprising two exhaust gas outlets each connected to an exhaust manifold of a group of at least one cylinder, said device comprising a charging device comprising a turbocompressor having a dual-inlet turbine connected to said exhaust gas outlets and an external air compressor, and at least one duct for partially transferring compressed air from the compressor to the turbine inlets, characterized in that the partial transfer duct is built into the cylinder head of the engine between an intake and an exhaust connected to the turbine inlets, and has throttling means controlling the circulation of transferred compressed air.
 2. The device as claimed in claim 1, wherein the partial transfer duct comprises a non-return flap.
 3. The device as claimed in claim 1 or 2, wherein it comprises at least two partial transfer ducts integrated into the cylinder head and connected to two exhaust outlets of said cylinder head in communication with the two turbine inlets.
 4. The device as claimed in claim 1, wherein the partial transfer duct connects the intake and exhaust of a same cylinder.
 5. The device as claimed in claim 1, wherein the partial transfer duct connects the intake of one cylinder and the exhaust of another cylinder.
 6. The device as claimed in claim 1, wherein the throttling means comprise proportional valves.
 7. The device as claimed in claim 6, wherein it comprises means for controlling the proportional valves.
 8. A method for controlling the amount of compressed air fed into the intake of a charged internal combustion engine, said engine comprising two exhaust gas outlets each connected to an exhaust manifold of a group of at least one cylinder, said device comprising a charging device with a turbocompressor having a dual-inlet turbine connected to said exhaust gas outlets and an external air compressor, and at least one duct for partially transferring compressed air from the compressor to the turbine inlets, wherein it consists of arranging said duct in the cylinder head of the engine between an intake and an exhaust connected to the turbine inlets, and introducing part of the compressed air leaving the compressor via said duct into the exhaust gas inlets of the turbine by controlling the circulation of compressed air transferred by the throttling means.
 9. The method as claimed in claim 8, wherein it consists of arranging at least two transfer ducts in the cylinder head and controlling the circulation of compressed air in each of the ducts by throttling means. 